Lori Daniels

Faculty of Forestry & Environmental Stewardship

Relevant Thesis-Based Degree Programs

Graduate Student Supervision

Doctoral Student Supervision

Dissertations completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest dissertations.

Disturbance synergies of bark beetles, woodborers and wildfire: investigating post-fire insect outbreak potential in the dry interior forests of British Columbia (2025)

Bark beetles (Coleoptera: Curculionidae: Scolytinae) and woodborers (Coleoptera: Buprestidae, Cerambycidae, Hymenoptera: Siricidae) are among the most important agents of tree mortality and decay in the phloem and sapwood of conifer tree species. Bark beetles and woodborers have been assumed to act independently, occupying distinct temporal niches throughout the death and decay processes of a conifer. However, interspecific interactions between bark beetles and woodborers may be more common than previously thought, with recent studies postulating that competition or predation from woodborers in the subcortical environment may be a notable, top-down constraint on bark beetle outbreaks. I evaluated the hypothesis that interspecific interaction between woodborers and bark beetles is a key driver of bark beetle irruptive dynamics, especially for pulse-driven irruptive species in the aftermath of broadscale forest disturbances. To address this, I studied Douglas-fir beetle (Dendroctonus pseudotsugae, hereafter DFB), a primary mortality agent of Douglas-fir, and the extent to which it interacts with woodborers following wildfires. Investigating the patterns of woodborer infestation post-fire, I found woodborers were frequent in stands with moderate fire-injury containing a living tree component, rather than stands following high-severity fire with near total mortality. Additionally, I found infestation was more likely in larger trees, suggesting woodborers selectively attack and kill mature conifers, which may otherwise survive their fire injuries. Investigating the extent of interspecific competition and/or predation by woodborers on bark beetles, I found DFB and woodborers were likely to attack trees with the same fire injury and stand characteristics. When co-infestation was high, woodborers successfully outcompeted DFB, indicating for the first time the result of interspecific interaction between these species following disturbance. Additionally, I found an apparent decoupling of pulse-driven DFB irruptions and fire that was associated with increasing disturbance rates across the Douglas-fir biome—an outcome consistent with widespread increases in woodborer populations over the same time period. My research has highlighted the need to quantify the role of top-down, interspecific pressures on the ability for bark beetles to outbreak, and how climate change may lead to the alteration of expected insect behaviour, particularly after widespread forest disturbances like wildfires.

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Landscape-level fire regime disruption: understanding and managing altered fire regimes in interior British Columbia, Canada (2025)

Prior to North American colonization, landscapes were governed by system-level feedbacks that maintained ecological resilience to disturbance. Increasingly frequent and extreme wildfire seasons in British Columbia (BC), Canada, are a symptom of the landscape-level disruption of historical fire regimes. Through three interrelated research questions, this dissertation characterizes the landscape-level disruption of fire regimes in southeastern BC and the ability of existing research and management systems to address these changes. Chapter 3 identifies transitions in historical fire regimes, describes the factors that drove them, and quantifies the resulting departures in fire frequency. I find that fire exclusion has significantly disrupted pre-colonial fire regimes, which transitioned through three phases from 1919 to 2019 to create fire deficits of 1–10 fires missed across forest types. Chapter 4 quantifies the accuracy and applicability of fuel type maps, explores the consequences of fuel misclassification, and identifies pathways to improve fuel representations. I find that fuel type maps do not accurately represent extant fuelbeds, particularly in dry interior ecosystems, mixedwood and deciduous stands, and post-harvesting conditions. Fuel typing mismatches stemmed from the low accuracy and availability of forest inventory data and the low applicability of existing fuel types. Chapter 5 assesses the state of landscape-fire-succession simulation modelling in North America and characterizes approaches on the frontier of this domain. I find that while succession is frequently represented as a complex mechanistic process, fire is often represented as a simplified hybrid process, leading to five common challenges and related priorities for next-generation development. Through this dissertation, three collective insights emerge: (1) The disruption of historical fire regimes has altered landscapes and degraded ecological resilience, exposing social-ecological systems to the threat of severe wildfires. (2) Adaptive management interventions that restore ecological resilience by reintroducing the role of fire as a process are justified to restabilize landscape dynamics. (3) Managing altered fire regime will require data and modelling systems evolve in their ability to represent fuels and fire-vegetation dynamics. Ultimately, transformative changes to systems and management are warranted to address the extent of fire regime departures and alter the current trajectory of landscapes as the climate steadily warms.

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Restor(y)ing fire landscapes : wildfire recovery, co-management and restoration in Secwepemcúl̓ecw (2023)

Worldwide, the increasing frequency and severity of ‘megafires’ poses a growing risk to people and ecosystems alike. While conservation scientists highlight the need to better understand how ecosystems are affected by and recover following megafires, Indigenous peoples are re-asserting jurisdiction to their lands and waters by leading the recovery and restoration of fire-affected territories. In this dissertation, conducted in collaboration with the Secwepemcúl̓ecw Restoration and Stewardship Society its member Secwépemc Nation communities, I examine how Secwépemc communities and territories are recovering from the 2017 ‘Elephant Hill’ megafire in British Columbia (BC), Canada, and the role of Indigenous-led restoration in restoring fire-adapted and fire-affected landscapes. Through semi-structured interviews, participant observation and plant community ecology methods, I document drivers and processes of both community-led and ecological recovery. Chapter 3 documents Secwépemc experiences of and engagement in wildfire management, with a focus on the collaborative governance of wildfire recovery. In describing the ‘joint leadership’ approach to recovery, this chapter identifies ‘lessons’ – successes, strengths, and challenges – to inform ongoing recovery and future wildfire response. Guided by the Secwépemc Declaration on the Understory, the fourth chapter analyzes the recovery of understory plant communities, with a focus on plants of high cultural significance to Secwépemc people. The high richness of culturally important plants recorded in areas that burned at low to moderate-severity, and in subalpine forests, highlights the strong potential of Indigenous fire stewardship to guide restoration and the ongoing eco-cultural importance of high-elevation landscapes to Secwépemc people. The fifth and final chapter describes Secwépemc Elder Ron Ignace’s concept of ‘walking on two legs’ (WO2L) to guide collaborative research and restoration in Secwepemcúl̓ecw and other Indigenous territories: the restoration of land by and to Indigenous peoples. These interdisciplinary and mixed-methods inquiries advance theories of collaborative environmental governance and the politics and production of knowledge, while responding to calls for a new megafire ecology to better understand the effects of large, high-severity wildfires on species, communities, and ecosystems. Collectively, this dissertation highlights the need to strengthen Indigenous leadership in wildfire management, and to support pathways of recovery that attend to the interconnections between land and community wellbeing.

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Fire in a dynamic social-ecological system: legacies and future of fire in British Columbia, Canada (2022)

Fire, people, and landscapes have dynamically coexisted through time in fire-dependent social-ecological systems, supported by diverse Indigenous stewardship. Today, however, fire is increasingly threatening peoples’ lives and livelihoods. This growing threat is partly attributed to an inadequate fire governance model that prioritizes fire control and fails to recognize the complexity of fire-dependent social-ecological systems across scales. In this dissertation, I take a collaborative and case study approach to explore these complex relationships in British Columbia (BC), Canada, at provincial and local scales over the last five centuries. By combining multiple methodologies, including historical document analysis, semi-structured expert interviews, place-based group interviews (forest walks), and tree-ring records, my dissertation demonstrates that the dominant fire governance model has cascading consequences for social and ecological systems through time. At the provincial scale, Indigenous stewardship was replaced by command-and-control fire governance in the late 19th and early 20th centuries, which was enforced by centralized government actors who continue to retain decision-making power over fire in BC. At the local scale, in a dry, Douglas-fir (Pseudotsuga menzeisii) dominated forest in the central interior of BC, the disruption of Indigenous stewardship in the 1870s altered the historical mixed-severity fire regime by eliminating highly frequent fire and landscape-level pyrodiversity. As a result, the dry forest today is more dense and likely to burn at uncharacteristic high severity, threatening enduring Indigenous values and livelihoods of adjacent communities. The 2017 fire season in BC was one such uncharacteristic season, which broke records for area burned (1.2 million hectares), number of people evacuated (~65,000), and fire suppression costs (~CAD$600 million) and prompted calls for a new paradigm of fire governance that includes Indigenous (and local) communities. To do so, however, this research demonstrates that Indigenous knowledge is uniquely situated within a place-based context, and it is imperative that decision-making power is redistributed to Indigenous peoples to ensure that context is respected. Ultimately, transformative change is needed to shift to a more equitable fire governance model that prioritizes proactive, Indigenous stewardship and ensures that resilience in a fire-dependent social-ecological system is defined and led by Indigenous peoples.

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Fire-resilient ecosystems: fire exclusion and selective harvesting degrade dry forests in British Columbia (2021)

In dry forests of southeastern British Columbia (BC) dense stands may be legacies of past high-severity fires and exist within the historical range of variability, or they may result from disruptions to historical fire regimes and indicate lost resilience. I conducted three dendrochronological studies that reconstructed the historical fire regimes and dynamics of these forests to discern the origin of high tree densities and guide ecosystem restoration to enhance forest resilience to fire and climate change. Historically, all 20 study stands were under an Indigenous-influenced, frequent, lower-severity fire regime. Moderate-severity fires initiated contemporary subcanopy cohorts, but ensuing fires, harvesting, and climate interacted to facilitate high tree densities. Fire exclusion prevented subsequent fires and allowed high densities to persist through time. In contrast to contemporary dense forests, historical stands were low-density and comprised of large, fire-tolerant trees; shade-intolerant ponderosa pine (Pinus ponderosa) and western larch (Larix occidentalis) dominated stand basal area. Historical selective harvesting removed the largest trees and favored shade-intolerant species. Contemporary stands are dominated by shade-tolerant Douglas-fir (Pseudotsuga menziesii var. glauca), with 1407% more trees, 143% more basal area, and 63% smaller quadratic mean diameter than historical stands. Western larch regeneration is absent and ponderosa pine regeneration is negligible. All contemporary trees are stressed: growth rates have declined, missing rings have increased, and many trees are dying. Canopy-dominant trees are more stressed than trees in lower canopy positions, most likely caused by competition with suppressed trees for soil moisture. Western larch was most stressed while Douglas-fir was least stressed, owing to differences in life history attributes. Dense stands are artefacts of human exclusion of fire and alterations to historical stand structures and composition, and represent degraded components of the dry forest matrix. To enhance resilience to fire and climate change, proactive forest management by thinning subcanopy trees will alleviate intense competition for soil moisture. Stands containing western larch should be prioritized to ensure its long-term persistence. Reintroducing fire provides necessary ecological feedbacks that will maintain resilience through time. Prescribed fires must be consistent with the reconstructed variation in historical frequency and severity, and will be enhanced by Indigenous knowledge.

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Drought influences mixed-severity fire regimes across temporal and spatial scales in the Montane Cordillera of Canada (2019)

Understanding historical fire-drought associations, particularly in forests with mixed-severity fire regimes, is a research and fire management priority in western North America. My thesis investigates how drought variation across temporal and spatial scales drove such fire regimes in the Montane Cordillera of Canada. I developed three-interrelated studies written as independent chapters, all of which used crossdated fire-scars to represent historical fire years. The first two studies test fire-drought associations using monthly adaptations of the Drought Code (DC) from Canada’s Fire Weather Index System. First, I compared three monthly drought codes during the 20th and 21st centuries for montane forests of southeast British Columbia. Accuracy of monthly DC increased after accounting for overwinter drying, early fire season starts, and effective precipitation. June-August drought codes were significantly associated with historical fires. Variation in fire-season drought influenced fire severity, connecting modern fire-weather indices with historical mixed-severity fire regimes. Second, I investigated how historical drought variation drove mixed-severity fire regimes in the same location by developing a tree-ring proxy reconstruction of summer DC. Comparing summer DC against a local summer Palmer Drought Severity Index provided a nuanced understanding of inter-annual fire-drought associations and moisture content among forest fuels, namely in deep compact organics in the soil and large woody fuels, versus the duff layer. Fire years were associated with coinciding and previous year summer drought; but limited by coinciding and previous year summer wet conditions. Summer moisture conditions during fire years likely influenced ignitions and led to variable combustion of forest fuels. The final study encompassed broader spatial coverage by including 17 fire-history sites across the Montane Cordillera, and by testing historical associations between climate and fire based on years with evidence of fire at multiple sites, i.e., fire synchrony. Fire synchrony was historically common, and associated with droughts at regional and subregional scales based on tree-ring proxy reconstructions of climate. My thesis provides information on drought as a driver of mixed-severity fire regimes across temporal and spatial scales. Ultimately, understanding how drought drove mixed-severity fire regimes across scales, helps fire managers anticipate how these fire regimes are shifting due to climate change.

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Understanding Disturbance, Facilitation, and Competition for Conservation of Whitebark Pine in the Canadian Rockies (2012)

Understanding forest resilience to novel disturbances and how tree interactions will be affected by global change is critical for predicting future forest composition. The widespread decline of the endangered whitebark pine (Pinus albicaulis) in the Canadian Rockies due to non-native white pine blister rust (Cronartium ribicola) and native mountain pine beetle (Dendroctonus ponderosae) and Ips sp. permitted examination of interactions between disturbances and tree responses in high-elevation forests. Disturbance severity was high with 20-90% whitebark pine mortality over 50 years in 16 stands. Basal annual increment (BAI) of whitebark pines prior to mortality from mountain pine beetles declined 46%, but only by 25% for those subsequently killed by blister rust and Ips sp.. Climate-growth relationships suggest blister rust increased sensitivity of whitebark pines to variation in summer precipitation, reducing resistance to beetles. The mortality of whitebark pine was used as an in-situ experiment simulating neighbour removal to test the stress-gradient hypothesis of tree interactions. Facilitation intensity, determined by comparing subalpine fir (Abies lasiocarpa) regeneration around live, top-killed, or dead adult whitebark pines, increased with elevation but depended on benefactor size and neighbourhood density. Large-diameter, top-killed whitebark pines were more facilitative than live trees, indicating thresholds in benefactor size, below which live, healthy trees were facilitators and above which they were competitors. Size thresholds were also found in interactions between adult trees where competition intensity increased between trees of greater diameter differences as indicated in BAI releases of subalpine fir after the death of neighbouring trees. Conversely, the importance of competition relative to other factors influencing growth increased between trees more similar in size and with abiotic stress. My results refine the stress-gradient hypothesis by demonstrating hierarchical influences on tree interactions. The predominant release from competition doubled subalpine fir’s BAI from the landscape average pre- disturbances compensating for the decline predicted by climate-growth relationships. Lack of regeneration and growth release in surviving whitebark pines and an abrupt shift in key variables suggest a regime shift to fir dominance and whitebark pine extirpation. Whitebark pine resilience was higher at sites of low abiotic stress and disturbance severity, relationships useful for conservation.

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Growth release of trees following fine-scale canopy disturbances in old-growth forests of coastal British Columbia, Canada (2008)

Growth release of trees following canopy disturbances is of interest to ecological scientists and forest managers. Using dendroecological techniques, I examined growth release of canopy and subcanopy trees following the formation of natural, fine-scale canopy gaps in old-growth, western red cedar-western hemlock forests of coastal British Columbia. I aimed to quantify detailed information on release of the three shade-tolerant tree species that constitute these stands: western red cedar (Thuja plicata), western hemlock (Tsuga heterophylla), and Pacific silver fir (Abies amabilis).As a first step, I calibrated the radial-growth averaging method to account for regional-scale variability and capture a more complete range of growth releases that may occur following the formation of fine-scale gaps in the study stands. A 25% threshold, 5-year moving average, and 10-year window emerged as appropriate parameters for detecting releases using radial-growth averaging. Basal area increment was also the most appropriate growth index for detecting releases. Establishing these empirically-based criteria was important for quantifying the magnitude and duration of releases.Tree diameter and growth rate prior to release were the most important predictors of the magnitude and duration of releases, but identity of the tree species and distance from the gap center were also important predictors. Western hemlock and Pacific silver fir were often growing slowly both in the canopy and subcanopy, giving them tremendous potential to release. For these species, releases were generally intensive and persistent. In contrast, western red cedar were often growing quickly both in the canopy and subcanopy, giving them less potential to release. Compared to western hemlock and Pacific silver fir, western red cedar releases were less intensive and persistent. Patterns related to distance from the gap center emerged for trees growing along the north-south axis of gaps. Regardless of species, increasing distance from the gap center resulted in decreasing magnitude and duration of releases. However, patterns for duration were complex, as the distance effect was greater for trees north of the gap center.Information on growth release of trees is useful for reconstructing the history of past canopy disturbances, elucidating mechanisms of tree species coexistence, and assessing and predicting stand changes due to forest management in coastal British Columbia.

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Master's Student Supervision

Theses completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest theses.

Plants are gifts: fire impact on plant diversity, richness and dominance at West Vaseux Lake, British Columbia (2026)

This research and its results share the ecological and cultural values of fire stewardship at West Vaseux Lake, located on the traditional territory of the Syilx Nation in British Columbia, Canada. In this research, the gap in knowledge of above-ground plant species composition was addressed across the five vegetation types: two areas treated with prescribed burns (2004 and 2013), and three unburned areas (closed forest, open forest, and grasslands). Using 240 quadrats among 24 transects, plant species were identified and classified as native, culturally significant, or introduced. Diversity metrics including, species richness, dominance and diversity (Simpson and Shannon-Wiener indices) and community composition were calculated to reveal key findings.There were 123 plant species, including 89 native, 25 culturally significant, and nine introduced identified across the study area. In the unburned areas, the closed forest unexpectedly showed high species richness due to shade tolerant plants and unique mosses and lichens. Burned areas exhibited high plant diversity and richness with low dominance. Fire-adapted culturally significant species such as arrowleaf balsamroot (Balsamorhiza sagittata) and bluebunch wheatgrass (Pseudoroegneria spicata) were found in abundance. The grasslands were dominated by antelope brush (Purshia tridentata) and prickly pear cactus (Opuntia fragilis) but had low species richness and diversity. Introduced species, particularly cheatgrass (Bromus tectorum), were most abundant in the grasslands.The findings of this research identify the critical need to reintroduce low-intensity fire to continue to enhance biodiversity and support culturally significant species, aligning with Syilx Ecological Knowledge and historical caretaking practices. Additionally, there is a need for collaborative restoration that prioritizes Syilx-led cultural burning to restore ecological resilience and kinship with fire. Recommendations include integrating Syilx decision making processes and principles into management of the study area. This would aid in correcting the colonial power imbalances and uphold Indigenous self-determination. Revitalizing cultural burning is essential for sustaining biodiversity, restoring cultural practices, and fostering reconciliation at West Vaseux Lake.

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Pining for change: effects of fire and fire surrogates on whitebark pine ecology, growth, and regeneration in Glacier National Park, BC (2025)

Whitebark pine (Pinus albicaulis), a high-elevation species critical to mountain ecosystems in western North America, is endangered in the United States and Canada due to white pine blister rust (Cronartium ribicola), mountain pine beetle (Dendroctonus ponderosae), and fire. Its relationship with fire is complex: while fire-intolerant, fire can reduce competition and promote regeneration. Consequently, prescribed fire and fire surrogates are used by land managers to restore its ecological functions.This thesis examines the role and efficacy of various treatment strategies—thinning, prescribed fire, a combination of thinning and prescribed fire, and wildfire—relative to untreated controls, on mature tree and regeneration dynamics of whitebark pine in the Bald Hills of Glacier National Park, BC. Field data were collected three years after prescribed fire, and five years after thinning and wildfire treatments.Widespread mortality of mature whitebark pine occurred regardless of treatment, with burned treatments showing 40–100% mortality and surviving trees experiencing increased mountain pine beetle infestation. White pine blister rust contributed to background mortality of nearly 20%. Fire severity, measured by Composite Burn Index (CBI), was highest in wildfire plots, followed by prescribed fire, and then thinning × prescribed fire treatments. Analysis of pre- and post-treatment ring widths revealed no significant release events among individual trees within the first four years, nor significant differences among treatments. Regeneration densities were generally higher in unburned treatments (control and thinning) than in fire-affected areas. Single-variable GLMs indicated negative effects of herb and fern cover, while multivariate models showed that shrub and regeneration cover positively influenced regeneration density. The findings underscore the complexity of fire effects on whitebark pine and emphasize the need for nuanced, site-specific management strategies. To optimize outcomes, mixed severity prescribed fire should be applied only in areas with dense overstory but few mature whitebark pine, while thinning should focus on trees clearly suppressed by competition. Additionally, thinning to remove surface fuels can reduce fire severity, and fire-damaged trees should be treated with anti-pine beetle pheromones to mitigate infestation risk. Re-measuring monitoring plots every five years is recommended to assess long-term treatment impacts on survival, growth, and regeneration.

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Short-term impacts of fuel treatments on above-ground forest carbon storage and stability in southeastern British Columbia (2025)

Me7 tsertsrep re nekect: me tsecentem re tmicw-kt (the forest will burn: we will restore our land) (2024)

Indigenous lands in interior British Columbia (BC), Canada are being impacted by increasingly large, fast-moving, high-severity wildfires due to climate change and an increase in vegetation (fuels) resulting from two centuries of settler-colonial land management. Despite disruptions from settler-colonial laws and policies, Stswecem'c Xget'tem First Nation (SXFN) has stewarded their Traditional Territory in south-central BC since time immemorial, including through frequent application of surface fire. SXFN communities have been repeatedly threatened by wildfires throughout the last two decades, inspiring SXFN to partner with the University of British Columbia in 2021 to quantify crown fire risk in their wildland-urban interface and explore forest stewardship solutions. I quantified fuel loads and potential fire behaviour in unceded dry SXFN forests with BC government legal objectives for mule deer winter range (MDWR) and old growth management (OGMA), then explored wildfire mitigation options through simulated fuel treatments. High fuel loads surrounding SXFN communities yielded predictions for high likelihood of crown fire under the 50th, 70th, 90th, and 97.5th percentiles of fire weather. Fuels data were altered to simulate fuel treatments that paired pruning and surface fuel abatement with varying intensities of thinning-from-below; two types of thinning complied with BC legal objectives for MDWR and OGMA, and another intensively thinned the smallest trees. I remodelled fire behaviour using the simulated fuel treatments and 90th percentile fire weather data and found that fuel treatments that complied with legal objectives for MDWR and OGMA reduced predictions of active crown fire but maintained high likelihood of intense passive crown fire. Comparatively, the intensive-thinning fuel treatment which would require an exemption to the legal objectives had the most efficacy in reducing crown fire predictions, but predictions for intense passive crown fire still dominated. These findings indicate that legal objectives for MDWR and OGMA should be critically revaluated, as they limit vital fuel reduction close to SXFN communities. Of utmost importance is that SXFN be able to lead the adaptive stewardship needed in these forests by using both local knowledge and western science. This work is urgent; it is not if, but when SXFN communities will next be threatened by wildfire.

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Fuel treatment efficacy in fire-prone forests of interior British Columbia, Canada (2023)

Extreme wildfire seasons have become a central challenge of forest management in western North America. In response to increasing wildfire risk, forest managers are proactively implementing fuel treatments. Although impacts of fuel treatments have been studied in the western United States, comparable research in the fire-prone forests of western Canada is lacking. In this thesis, I used two approaches to assess the efficacy of alternative fuel treatments to mitigate fire behaviour and effects in the seasonally dry forests of southeastern British Columbia, Canada. I partnered with five community forests in the Kootenay region and measured key components of the wildland fuelbed in forest stands before and after treatment. For the first approach, I used the pre-treatment field data as a baseline and simulated 16 alternative fuel treatment scenarios that spanned the range of thinning, pruning, and surface fuel load reduction combinations being implemented in the region. I modelled stand-level fire behavior (i.e., passive and active crown fire) and effects (i.e., tree mortality) under these simulated stand conditions using Fuels Management Analyst Plus (FMA), and fitted meta-models to assess the treatment impacts. For the second approach, I categorized the fuel treatments implemented by the community forests into five different types based on thinning, pruning, and residue fuel management. I examined the variability of key stand attributes within fuel treatment types. Then, I determined the impacts of the five treatment types on fire behaviour and effects metrics obtained from FMA. Based on results from both approaches, removal of small trees reduced risk of passive crown fire, but concurrent removal of larger trees was necessary to reduce risk of active crown fire. Pruning had minimal impact on mitigating potential of passive crown fire. Ameliorating residue fuels through chipping or pile burning reduced risk of passive crown fire; however, the impacts of chipping on residual tree mortality remains a potential concern. This work provides the first insights into the efficacy of fuel treatments in the Kootenay region and will help forest managers make more informed wildfire management decisions.

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Freezing to death in a warming climate: drivers of yellow-cedar decline on Haida Gwaii (2019)

The global rise in temperature and associated changes in climate have led to decline of forests around the globe, across multiple species and ecosystems. This includes yellow-cedar (Callitropsis nootkatensis) decline, which is one of the most severe in North America. I found abundant evidence of tree decline and mortality of yellow-cedar on Haida Gwaii across multiple watersheds and over a range of elevations. The decline on Haida Gwaii parallels the broader yellow-cedar decline in terms of spatial distribution, symptoms, magnitude and timing. Nevertheless, the proposed drivers on the mainland may not adequately explain the decline on Haida Gwaii, due to the more temperate climate and lack of persistent snowpack. I investigated several possible drivers both at the local and regional scale. My results are inconsistent with stand dynamics as a driver of elevated decline and mortality. Neither increased competition, nor aging of a cohort explains the decline. Onset of basal area increment decline and mortality have been accumulating over time, with increased rates since the 1980s. Alternatively, the magnitude and timing of the decline is consistent with well-documented multi-decadal variations and long-term directional trends in regional climate. I found patterns of divergent growth and divergent response to climate among yellow-cedars at the same sites. Yellow-cedars affected by decline were decreasing in growth and negatively associated with warmer drier winter conditions. Whereas, yellow-cedars not affected by decline were increasing in growth and positively associated with warmer growing season temperatures. The limiting factors for declining trees, warm dry winter conditions, are consistent with the hypothesis from the mainland that climate warming has led to root freezing. However, compared to drivers of yellow-cedar decline on the mainland, snowpack plays a less important role on Haida Gwaii. Warming temperatures likely have a more direct effect. I propose warmer winter temperatures have led to a combination of decreased cold-hardening and earlier dehardening, in conjunction with increased frequency of thaw-freeze cycles and freeze events during otherwise milder winters. This exposes yellow-cedar’s fine roots to varying degrees of freezing damage over multiple winter thaw-freeze cycles, causing physiological stress, tree decline and eventual death.

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Historical and contemporary disturbance regimes in central interior dry forests of British Columbia (2019)

Accurate historical reconstructions of disturbance regimes are necessary because current approaches toward more sustainable forest practices attempt to model forest management after historical disturbance regimes and recovery processes. Using dendrochronological analyses, I characterized both the historical fire regime and outbreaks of western spruce budworm (Choristoneura occidentalis Freeman) within a dry mixed-conifer forest to assess whether contemporary regimes are outside the historical range of variation. By determining the degree of change between the historical fire regime and the current, I provide insight into the potential consequences that fire suppression has had on resilience to fire and budworm. Historical fires burned in 23 different years from 1619 to 1943 with a mean interval of 15 years. Beginning in the later part of the 19th century fire patterns changed, such that the current fire-free period drastically exceeds the historical maximum fire-free intervals at all but 1 plot. Fire scars and post-fire cohorts varied among plots and indicated fires burned at mixed severities through time and space. Eight western spruce budworm outbreaks initiated between 1800 and 2001 with mean a mean duration of 14 years and mean return interval of 29 years. Outbreaks of a range of durations, frequencies, and severities were well represented throughout the record with no discernable trend in time. There was no significant difference between the number and timing of infestations initiating in plot canopies or subcanopies. The simple linear regression analyses determined plot-level subcanopy tree density (R² = 0.02; p = 0.43,) and the ratio of subcanopy to canopy tree densities (R² = 0.02; p = 0.48) to be poor predictors of severity during the outbreak from 2001 to 2011. It is strongly suspected that in the absence of fire in the 20th century, the forest has become denser and has lost a substantial degree of structural diversity. In addition, accumulations of ladder and surfaces fuels have also occurred and leave the forest at increased risk of a high-severity stand-replacing fire and less resilient to budworm attack.

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Humans, climate, and an ignitions-limited fire regime at Vaseux Lake (2017)

This study investigated the role of human land use and climate as drivers of the historical fire regime of a 400ha protected area in the Okanagan region of British Columbia. I used fire scars and forest demography data to reconstruct spatiotemporal patterns in fires from 1714 - 2013. I also used paleo-climate reconstructions derived from tree ring series to evaluate whether historical fire-climate relationships changed with the displacement of indigenous peoples. Fire patterns were closely coupled with the human history of the study area. Fires were more frequent, less synchronous, and burned earlier in the season when indigenous people were stewarding the study area traditionally. Logistic regression showed that fires were also twice as likely during this period, and that topographic factors were not a significant control of the fire regime. Analysis of fire-climate relationships revealed that human land use superseded the effects of inter-annual and decadal-scale climate as a driver of historical fires. Fires occurred during a variety of conditions when indigenous people were stewarding the study area traditionally, while fires after indigenous people were displaced were associated with El Niño years, which tend to bring warm/dry conditions to the region. The historical fire regime at Vaseux was of mixed-severity in time and space, and this variability helped generate a complex forest structure. Historical fires acted to control tree establishment and mortality, and the forest is now denser than it was historically due to reduced fire frequency in the late 20th century. Continued infilling could shift the fire regime towards a greater component of high-severity fire. The results suggest that indigenous traditional land stewardship was the dominant control of historical fire dynamics at Vaseux. Managers wishing to preserve habitat and forest structures generated by the historical fire regime will need to account for the influence of indigenous burning, and modern lightning intervals will not be a sufficient baseline for setting treatment intervals. Proactive management designed to maintain a fire regime of frequent mixed-severity fires will be necessary to promote ecological resilience in an uncertain future.

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The effects of single-objective management on disturbances in central interior dry forests of British Columbia (2017)

Mule deer are an important game species, and have become the focus of applying a particular silvicultural treatment that enhances habitat while allowing timber harvesting. Mule deer winter range management (MDWRM) involves the proportional removal of trees based on their diameter and abundance resulting in a multilayered, Douglas-fir dominated forest with a clumpy tree distribution. I assessed changes in forest stand attributes brought about by MDWRM through time and how these attributes related to stand susceptibility to the western spruce budworm, Douglas-fir beetle, and wildfire using a randomized complete block single factor mixed-effects model with subsampling. In the short-term, MDWRM significantly changed (p0.05) forest stand attributes by decreasing sub-canopy tree density and basal area, canopy cover, leaf area index, and increasing large surface fuel load. In the long-term, most attributes recovered to untreated levels. Relative to untreated stands, treated stands maintained a multilayered structure and an abundance of Douglas-fir trees thus their susceptibility to the western spruce budworm did not change through time. In the short-term, a reduction in mature host-tree density lowered susceptibility to the Douglas-fir beetle. With subsequent forest recovery, long-term susceptibility did not differ relative to untreated stands. In the treated stands the likelihood of crown fire was greater shortly after than longer after treatment. This was likely due to more large surface fuels immediately following treatment. In addition, I extrapolated the effects of MDWRM across eligible stands of interior British Columbia in a hypothetical simulation to evaluate the current and forecasted landscape-level fire risk. The forecasted forest under widespread application of MDWRM resulted in a homogenized landscape dominated by low fire risk. Further, widespread application of MDWRM may result in a fire resilient landscape, but with consequences for other ecological processes. The present study contributes to our understanding of the relationship between single-objective management and subsequent stand susceptibility to biotic and abiotic disturbances. I concluded that understanding this relationship should play an important role in responsible resource management.

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Fire history and climate-fire relations in Jasper National Park, Alberta, Canada (2014)

Historical fire regime of the Darkwoods: quantifying the past to plan for the future (2011)

Decay Dynamics of Coarsewood Habitat in Old-growth Spruce and Pine Stands in the Rocky Mountain Foothills (2010)

This thesis presents research on the decay dynamics of coarsewood wildlife habitat in the foothills of the Rocky Mountains, west-central Alberta. The study sites were located in permanent sample plots in five Picea glauca and five Pinus contorta old-growth stands. I combined field sampling, dendrochronology, and permanent sample plot data to characterize snags and logs. I used a functional classification scheme to assess the potential wildlife habitat value of snags and logs. The study had two main objectives: (1) to quantify the magnitude of error in dendrochronological work on decayed wood and (2) to assess the accumulation and persistence of snags and logs and their potential functions as wildlife habitat.I used permanent plot data to verify the accuracy of year-of-death estimates obtained by crossdating snags and logs. I obtained YOD estimates from 71 snags and 54 logs. Most YOD dates occurred within the observed interval of death dates from the permanent plot data (54%-80%, grouped by species and coarsewood type) and most remaining dates preceded the interval of death. Overall, the magnitude of error in YOD estimates increased with time since death.I located 322 snags and 405 logs. Mean densities were 403 snags/ha and 506 logs/ha. Snags and logs in intermediate decay classes were the most common, and I hypothesize that most snags reach decay class 4 or 5, rot at the base and fall over, rather than decaying completely in situ. Coarsewood persisted for many decades after death: estimated time since death of the oldest snag and log was 180 and 175 years, respectively. Time since death varied significantly across decay class, but the range of YOD dates in each decay class was so broad that decay class was not a reliable indicator of approximate time since death. Most observations of habitat functions were limited to one of five functional types. Less than 1% of snags and 4% of logs provided four or more habitat functions.Given the longevity of coarsewood in these stands, management plans must take a long-term view in order to maintain levels of coarsewood that are within the natural range of variability.

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